In the known lithographic process, especially in the proximity exposure lithography process, due to the reaction heat or light excitation during the exposure process, as illustrated in FIG. 1a, an organic solvent 2 etc. remaining in a photoresist 1 evaporates to a mask 3 and condenses as an organic coagulation 4 on the surface of the mask 3. The contact angle θ between the mask 3 and the organic coagulation 4 is generally less than 90 degrees, as illustrated in FIG. 1b, so that the organic coagulation has a greater infiltration capacity to the mask and it is not easy for the organic coagulation to fall. The organic coagulation adhering to the surface of the mask will contaminate the surface of the mask, seriously affecting the exposure accuracy. In addition, the frequency for cleaning the mask will be increased due to the contamination of the surface of the mask by the organic coagulation, which is not conducive to long-term continuous production.
At present, an organic coagulation processing apparatus is generally installed in an exposed area, the apparatus can decompose the organic coagulation coagulating on the surface of the mask, and then the decomposed organic coagulation can be brought out of the exposure chamber by means of a gas system in the apparatus, thereby reducing the contamination of the mask by the organic coagulation during the exposure process.